U.S. patent number 6,043,810 [Application Number 08/981,177] was granted by the patent office on 2000-03-28 for digitizer controller.
This patent grant is currently assigned to Samsung Electronics, Co., Ltd.. Invention is credited to Byoung-kwon An, Do-youn Kim.
United States Patent |
6,043,810 |
Kim , et al. |
March 28, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Digitizer controller
Abstract
A digitizer controller includes a panel drive signal generator
(10), a reference voltage generator (12), a first multiplexer (14)
for selectively outputting either a panel drive signal or a
reference voltage signal, a 4-channel driving portion (16) for
generating a channel driving signal which is provided to each
corner of a panel, a third multiplexer (26) for selectively
outputting one of the finger touch signals and a stylus signal
output from a stylus, a band pass filter, a rectifier (30) for
rectifying the output of the band pass filter, a low pass filter
(38) for detecting a substantial direct current component from the
output of the rectifier (30), an analog-to-digital converter (44)
for outputting the output of the low pass filter in synchronization
with a panel driving control signal as a coordinates signal, and an
interface (46). Therefore, the digitizer controller can be adopted
to each of the stylus, finger touch and touch panel type
digitizers, and in implementing a semiconductor integrated circuit,
reliability is provided and power consumption is lowered.
Inventors: |
Kim; Do-youn (Seoul,
KR), An; Byoung-kwon (Kunpo, KR) |
Assignee: |
Samsung Electronics, Co., Ltd.
(Suwon, KR)
|
Family
ID: |
27483066 |
Appl.
No.: |
08/981,177 |
Filed: |
December 12, 1997 |
PCT
Filed: |
June 12, 1996 |
PCT No.: |
PCT/KR96/00089 |
371
Date: |
December 12, 1997 |
102(e)
Date: |
December 12, 1997 |
PCT
Pub. No.: |
WO96/42068 |
PCT
Pub. Date: |
December 27, 1996 |
Foreign Application Priority Data
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Jun 12, 1995 [KR] |
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95-15442 |
Jul 20, 1995 [KR] |
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95-21316 |
Dec 26, 1995 [KR] |
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95-56423 |
Dec 30, 1995 [KR] |
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95-69704 |
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Current U.S.
Class: |
345/173 |
Current CPC
Class: |
G06F
3/045 (20130101) |
Current International
Class: |
G06F
3/033 (20060101); G09G 005/00 () |
Field of
Search: |
;345/173,179,180 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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89118974 |
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Apr 1990 |
|
EP |
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90303005 |
|
Oct 1991 |
|
EP |
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92306151 |
|
Feb 1993 |
|
EP |
|
93108594 |
|
Dec 1993 |
|
EP |
|
Primary Examiner: Hjerpe; Richard A.
Assistant Examiner: Laneau; Ronald
Attorney, Agent or Firm: Marger Johnson & McCollom,
P.C.
Claims
What is claimed is:
1. A digitizer controller (100) for applying a 4-channel driving
signal for driving the four corners of a panel (200) in response to
a panel driving control signal befitting a stylus type and a touch
panel type digitizer and outputting coordinate data by recognizing
a contact position by a stylus or a finger, said digitizer
controller comprising:
a panel drive signal generator (10) for receiving a clock signal
having a predetermined first frequency and generating a panel drive
signal having a predetermined second frequency and required in
stylus and finger touch modes;
a 4-channel driving portion (16) for receiving said panel drive
signal provided from said panel drive signal generator (10) and
generating a channel driving signal which is provided to each
corner of said panel (200) in response to said panel driving
control signal according to an operation mode;
a current-voltage converter (18) for detecting a change in current
in or out of each corner of said panel (200);
a differential amplifier (20) for generating a differential signal
of four channels corresponding to a differential component between
the output of said current-voltage converter (18) and the channel
driving signal provided from said 4-channel driving portion (16) in
said finger touch mode;
a second multiplexer (22) for sequentially selecting the
four-channel differential signal of the output from said
differential amplifier (20) to output the selected signal as a
finger touch signal;
a third multiplexer (26) for selectively outputting one of the
finger touch signal output from said second multiplexer (22) and a
stylus signal output from a stylus in response to a mode selection
signal indicating the stylus or the finger touch mode;
a fourth multiplexer (34) for selectively outputting one of a
predetermined second reference voltage and the touch panel signal
output from said panel (200) in response to the mode selection
signal;
a band pass filter (28) for filtering the frequency component of
the panel drive signal from the output of said third multiplexer
(26);
a rectifier (30) for rectifying the output of said band pass filter
(28);
a fifth multiplexer (36) for selectively outputting one of the
outputs of said rectifier 30 and said fourth multiplexer (34) in
response to the mode selection signal;
a low pass filter (38) for detecting a substantial direct current
component from the output of said fifth multiplexer (36);
an analog-to-digital converter (44) for converting the output of
said low pass filter (38) into a digital signal in synchronization
with the panel driving control signal to output as a coordinates
signal; and
an interface (46) for receiving control commands provided from a
microprocessor, generating the mode selection signal indicating the
stylus, the finger touch or the touch panel mode by interpreting
the received control command and the panel driving control signal
corresponding to the selected mode, and transmitting the
coordinates signal provided from said analog-to-digital converter
44 to the microprocessor.
2. The digitizer controller of claim 1, wherein said differential
amplifier (20) is provided with four channel driving blocks
(20a-20b), each amplifying the difference of one of the channel
driving signals and one of the current-voltage converted channel
driving signals.
3. The digitizer controller of claim 1, further comprising a
preamplifier (24) for amplifying the finger touch and the stylus
signals by a predetermined gain, respectively, to provide to one of
said third multiplexer (26) and said fourth multiplexer (34).
4. The digitizer controller of claim 1, further comprising:
a direct current amplifier (40) having at least two direct current
amplifiers (40b and 40c) for amplifying the output of said low pass
filter (38) by a separate gain according to the operation mode;
and
a sixth multiplexer (42) for selecting one of the outputs of said
direct current amplifiers (40b and 40c) in response to the mode
selection signal to provide the selected output to said
analog-to-digital converter (44).
5. The digitizer controller of claim 1, further comprising a
digital-to-analog converter (32) for digital-to-analog converting
the control signal provided from said microprocessor to apply the
converted control signal as a frequency characteristic control
signal of said band pass filter (28).
6. The digitizer controller of claim 1, wherein said panel drive
signal generator (10) further generates a pilot signal having a
substantially same frequency as that of the panel drive signal
which is provided to said band pass filter (28) during automatic
frequency characteristic control.
7. The digitizer controller of claim 1, wherein said
current-voltage converter (18) is configured with variable
resistors so that sensitivity of the current-voltage conversion can
be adjusted.
8. The digitizer controller of claim 1, wherein in said low pas
filter (38) removal of noise components and conversion to direct
current is easily achieved since the bandwidth thereof is
narrow.
9. The digitizer controller of claim 1, wherein said interface (46)
comprises:
a data latch (46b) for latching the control command provided from
said microprocessor;
a data buffer (46d) for inputting a digitally converted coordinates
value provided from said analog-to-digital converter (44) and
outputting the input coordinates value to said microprocessor;
a command decoder (46a) for receiving the control command provided
from said data latch (46b) and generating the mode selection
signal, the panel driving control signal, the channel selection
signal and the frequency characteristic control signal necessary
for control of said digitizer controller; and
an address decoder (46c) for receiving an address signal provided
from said microprocessor and generating signals for activating said
data latch (46b) and the data buffer (46d).
10. The digitizer controller of claim 1, wherein said panel driving
signal generator (10) comprises:
a D-flip flop (120) for receiving a clock signal and generating a
(n-1)th signal divided by n, wherein n is an integer, wherein the
(n-1) divided signal is generated, each being synchronized from the
first clock signal to the (n-1)th clock signal in a sequential
clock signal string of the corresponding number to division ratio
n;
a ladder portion (124) for generating a pseudo sinusoidal signal by
weight-calculating the (n-1) division signals according to a
predetermined resistance value; and
a band pass filter (28) for generating the panel drive signal which
is a substantial sine wave by band-pass-filtering the pseudo
sinusoidal signal provided from said ladder portion (124).
11. The digitizer controller of claim 1, wherein said panel driving
control signal generator (74) comprises:
a first counter (740) for generating a first count signal by
counting the clock signal at a predetermined first counting
ratio;
a second counter (742) for binary-counting the first count signal
provided from said first counter (740) to output the binary-counted
signal as a second signal;
an inverting portion (744) having two inverters (744a and 744b) for
respectively inverting the first and second count signals each
provided from said first and second counters (740 and 742);
an OR gate (746) for OR-ing the first and second count signals;
and
a signal selecting portion (748) for receiving the first and second
count signals respectively provided from said first and second
counters (740 and 742), the inverted first and second count signals
provided from said inverting portion (744) and a signal output from
said OR gate (746) and generating a panel driving control signal
corresponding to each mode in response to the mode selection
signal,
wherein said signal selecting portion (748) outputs the first and
second count signals respectively provided from said first and
second counters (740 and 742), the inverted first and second count
signals provided from said inverting portion (744) and a signal
output from said OR gate (746) in the stylus and the touch panel
modes and the signal provided from said OR gate (746) in the finger
touch mode.
12. The digitizer controller of claim 1, further comprising:
a counting portion (720) for counting the clock signal having a
predetermined period at a predetermined first count ratio to output
a first pulse signal;
a counter (722b) for counting the first pulse signal output from
said counting portion at a predetermined second count ratio, by
starting the counting operation according to a tip signal of the
stylus; and
a power slip signal generator (722) for determining whether the
idle status of the stylus continues over a predetermined time by
AND-ing a second pulse signal output from said counter (722b) and
the tip signal of the stylus and generating a power slip signal for
controlling power consumption if the idle status continues over the
predetermined time period,
wherein said interface (46) enters a power saving mode in response
to the power slip signal provided from said power slip signal
generator (722).
13. An integrated semiconductor circuit comprising the digitizer
controller claimed in claim 1.
14. A digitizer controller which applies a 4-channel driving signal
for 1driving the four corners of a panel (200) in response to a
panel driving control signal befitting a stylus type, a touch panel
type and a finger touch type and outputs coordinated data by
recognizing a contact position by a stylus, a pen or a finger, said
digitizer controller comprising:
a panel drive signal generator (10) for receiving a clock signal
having a predetermined a first frequency and generating a panel
drive signal having a predetermined second frequency and required
in stylus and finger touch modes;
a reference voltage generator (12) for generating a reference
voltage signal having a predetermined reference level required in a
touch panel mode;
a first multiplexer (14) for selectively outputting one of the
reference voltage signal provided from said reference voltage
generator (12) and the panel drive signal provided from said panel
drive signal generator (10) in response to a mode selection signal
indicating the stylus, finger touch or touch panel mode;
a 4-channel driving portion (16) for receiving the output of said
first multiplexer (14) and generating a channel driving signal
which is provided to each corner of said panel (200) in response to
said panel drive control signal according to an operation mode;
a current-voltage converter (18) for detecting change of current in
or out of each corner of said panel (200);
a differential amplifier (20) for generating a differential signal
of four channels corresponding to differential component between
the output of said current-voltage converter (18) and the channel
driving signal provided from said 4-channel driving portion (16) in
said finger touch mode;
a second multiplexer (22) for sequentially selecting the
four-channel differential signal of output from said differential
amplifier (20) to output the selected signal as a finger touch
signal;
a third multiplexer (26) for selectively outputting one of the
finger touch signal output from said second multiplexer (22) and a
stylus signal output from a stylus in response to the mode
selection signal;
a fourth multiplexer (34) for selectively outputting one of a
predetermined reference voltage and the touch panel signal output
from said panel (200) in response to the mode selection signal;
a band pass filter (28) for filtering the frequency component of
the panel drive signal from the output of said third multiplexer
(26);
a rectifier (30) for rectifying the output of said band pass filter
(28);
a fifth multiplexer (36) for selectively outputting one of the
outputs of said rectifier 30 and said fourth multiplexer (34) in
response to the mode selection signal;
a low pass filter (38) for detecting substantial direct current
component from the output of said fifth multiplexer (36);
an analog-to-digital converter (44) for digital-converting the
output of said low pass filter (38) into a digital signal in
synchronization with the panel driving control signal to output as
a coordinates signal; and
an interface (46) for receiving a control command provided from a
microprocessor, generating the mode selection signal indicating the
stylus, the finger touch or the touch panel mode by interpreting
the received control command and the panel driving control signal
corresponding to the selected mode, and transmitting the
coordinates signal provided from said analog-to-digital converter
44 to the microprocessor.
15. The digitizer controller of claim 14, wherein said differential
amplifier (20) is provided with a plurality of channel driving
blocks corresponding to the number of the channel driving signals,
each amplifying the difference of one of the channel driving
signals and one of the current-voltage converted channel driving
signals.
16. The digitizer controller of claim 14, further comprising
pre-amplifier (24) for amplifying the finger touch signal, the
stylus signal and the touch panel signal at a predetermined
amplification rate, respectively, to provide to wither said third
multiplexer (26) and said fourth multiplexer (34).
17. The digitizer controller of claim 14, further comprising:
a direct current amplifier (40) having three direct current
amplifiers for amplifying the output of said low pass filter (38)
at separate gains according to the operation mode, and
a sixth multiplexer (42) for selecting one of outputs of said
direct current amplifiers in response to the mode selection to
provided the selected output to said analog-to-digital converter
(44).
18. The digitizer controller of claim 14, further comprising a
digital-to-analog converter (32) for converting the digital control
signal provided from said microprocessor into an analog signal to
apply the converted control signal as a frequency characteristic
control signal of said band pass filter (28).
19. The digitizer controller of claim 14, wherein said panel drive
signal generator (74) further generates a pilot signal having the
substantially same frequency as that of the panel drive signal
which is provided to said band pass filter (28) during automatic
frequency characteristic control.
20. The digitizer controller of claim 14, wherein said
current-voltage converter (18) is configured with variable
resistors so that sensitivity of the current-voltage conversion can
be adjusted.
21. The digitizer controller of claim 14, wherein in said low pass
filter (38) removal of noise components and conversion to direct
current is easily achieved since bandwidth thereof is narrow.
22. The digitizer controller of claim 14, wherein said panel drive
signal generator (74) comprises:
a D-flip flop (120) for receiving a clock signa and generating a
(n-1)th signal divided by n, wherein n is an integer, wherein the
(n-1) divided signal is generated, each being synchronized from the
first clock signal to the (n-1)th clock signal in a sequential
clock signal string of the corresponding number to division ratio
n;
a ladder portion (124) for generating pseudo sinusoidal signal by
weight-calculating the (n-1) division signals according to a
predetermined resistance value; and
a band pass filter (28) for generating the panel drive signal which
is a substantial sine wave by band-pass-filtering the pseudo
sinusoidal signal provided from said ladder portion (124).
23. An integrated semiconductor circuit comprising the digital
controller claimed in claim 14.
24. A method for driving a panel befitting a finger touch type
digitizer comprising the steps of:
applying channel driving signals having the same potential to each
corner of said panel (200);
detecting the change in current generated by the contact of a
finger on said panel (200) in or out of each corner of said panel
(200), and converting the detected change in current changing into
a change in voltage;
detecting differential signals corresponding to the difference of
the current-to-voltage converted signal and the channel driving
signal;
sequentially selecting the differential signals at a predetermined
period and time-division multiplexing the selected differential
signals; and
determining the contact position of the finger according to the
size of the multiplex differential signal.
25. A driving apparatus of a finger touch type digitizer
comprising:
a panel drive signal generator (10) for generating a panel drive
signal required in a finger touch mode;
a 4-channel driving portion (16) for receiving the panel drive
signal and generating a 4-channel driving signal of substantially
the same electric potential which is provided to the four corners
of a panel (200);
a current-to-voltage converter (18), interposed between said
4-channel panel driving portion (16) and said panel (200), for
detecting a change in current in or out of each corner of said
panel (200) when the finger contacts said panel (200);
a differential amplifier (20) for generating a difference of the
4-channel driving signal and the current-to-voltage conversion
value from said current-to-voltage converter (18);
a multiplexer (22) for sequentially selecting the four-channel
differential signal of the output from said differential amplifier
(20) at a predetermined period to output the selected signal;
a band pass filter (28) for detecting a frequency component of the
panel drive signal from the output of said multiplexer (22);
a low pass filter (38) for extracting a substantial direct current
component from the output of said band pass filter (28); and
an analog-to-digital converter (44) for converting the output of
said low pass filter (38) into a digitizer signal in
synchronization with the selected period of said multiplexer
(22).
26. A method of adjusting the frequency characteristic of a band
pass filter (28) for band-pass-filtering a frequency component of a
panel drive signal from a finger touch signal provided from a panel
(200) or a stylus signal provided from a stylus in a digitizer
controller befitting a stylus type and a finger touch type, said
method comprising the steps of:
inputting a pilot signal having substantially the same frequency as
the panel drive signal to said band pass filter (28) and
continuously converting within a predetermined range an adjusting
signal for adjusting the frequency characteristic of said band pass
filter (28);
comparing the signal from said band pass filter (28) and
determining a value of the adjustment signal having the maximum
amplitude of the detected signal; and
setting a frequency characteristic of said band pass filter (28)
according to the determined adjustment signal.
27. An apparatus for adjusting the frequency characteristic of a
band pass filter (28) for band-pass-filtering a frequency component
of a panel drive signal from a finger touch signal provided from a
panel (200) or a stylus signal provided from a stylus in a
digitizer controller befitting a stylus type and a finger touch
type digitizer, said apparatus comprising:
a panel drive signal generator (10) for generating a pilot signal
having substantially the same frequency as that of a panel drive
signal to provide to said band pass filter (28);
a digital-to-analog converter (32) for converting an analog
adjustment signal applied from a microprocessor into an digitizer
signal and applying the converted signal as a signal for adjusting
the frequency characteristic of said band pass filter (28);
an analog-to-digital converter (44) for detecting the amplitude of
a signal from said band pass filter (28);
a microprocessor for generating the adjustment signal changing
within a predetermined range to change the frequency characteristic
of said band pass filter (28) to provide the generated adjustment
signal to said digital-to-analog converter (32), determining an
adjustment signal corresponding to a signal having the maximum
amplitude among the band-pass-filtered signals from the changing
adjustment signal within the predetermined range, and providing the
determined adjustment signal as a frequency characteristic
adjustment signal of said band pass filter (28).
28. An interface (46) for transmitting control commands generated
from a microprocessor to peripheral devices and controlling the
transmission of the data provided from the peripheral devices to
said microprocessor, said interface comprising:
a data latch (46b) for latching the control command provided from
said microprocessor;
a data buffer (46d) for inputting the data provided from said
peripheral devices and outputting the input data to said
microprocessor;
a command decoder (46a) for receiving the control command provided
from said data latch (46b) and generating various control signals
necessary for control of said peripheral devices; and
an address decoder (46c) for receiving an address signal provided
from said microprocessor and generating signals for activating said
data latch (46b) and the data buffer (46d).
29. An apparatus for generating a sinusoidal signal comprising:
a D flip-flop (120) for receiving a clock signal and generating a
(n-1)th signal divided by n, wherein n is an integer, and wherein
the (n-1) divided signal is generated, each being synchronized from
the first clock signal to the (n-1)th clock signal in a sequential
clock signal string of the corresponding number to division ratio
n;
a ladder portion (124) for generating a pseudo sinusoidal signal by
weight-calculating the (n-1) division signals according to a
predetermined resistance value; and
a band pass filter (28) for generating the panel drive signal which
is a substantial sine wave by band-pass-filtering the pseudo
sinusoidal signal provided from said ladder portion (124).
30. A panel driving control signal generator for controlling the
generation of a 4-channel driving signal for driving the four
corners of a panel (200) befitting a stylus type, a touch panel
type and a finger touch type digitizer, said generator
comprising:
a first counter (740) for generating a first count signal made by
dividing a clock signal at a predetermined first count ratio;
a first counter (740) for generating a first count signal by
counting the clock signal at a predetermined first counting
ratio;
a second counter (742) for binary-counting the first count signal
provided from said first counter (740) to output the binary-counted
signal as a second signal;
an inverting portion (744) having two inverters (744a and 744b) for
respectively inverting the first and second count signals each
provided from said first and second counters (740 and 742);
an OR gate (746) for OR-ing the first and second count signals;
and
a signal selecting portion (748) for receiving the first and second
count signals respectively provided from said first and second
counters (740 and 742), the inverted first and second count signals
provided from said inverting portion (744) and a signal output from
said OR gate (746) and generating a panel driving control signal
corresponding to each mode in response to the mode selection
signal,
wherein said signal selecting portion (748) outputs the first and
second count signals respectively provided from said first and
second counters (740 and 742), the inverted first and second count
signals provided from said inverting portion (744) and a signal
output from said OR gate (746) in the stylus and the touch panel
modes and the signal provided from said OR gate (746) in the finger
touch mode.
31. A power saving apparatus which prevents power consumption of a
digitizer controller in a state when a stylus is not used in a
stylus type digitizer, said apparatus comprising:
a counting portion (720) for counting the clock signal having a
predetermined period at a predetermined first count ratio to output
a first pulse signal;
a counter (722b) for counting the first pulse signal output from
said counting portion at a predetermined second count ratio, by
starting counting operation according to a tip signal of the
stylus; and
a power slip signal generator (722) for determining whether the
idle status of the stylus continues over a predetermined time
period by AND-ing a second pulse signal output from said counter
(722b) and the tip signal of the stylus and generating a power slip
signal for controlling power consumption if the idle status
continues over the predetermined time period,
wherein said interface (46) enters a power saving mode in response
to the power slip signal provided from said power slip signal
generator (722).
Description
TECHNICAL FIELD
The present invention relates to a digitizer controller, and more
particularly, to a digitizer controller which can be implemented in
an integrated circuit of a semiconductor device and applied to
stylus type, finger touch type and touch panel type digitizers.
BACKGROUND ART
Personal computers, portable transmitters, personal information
processor, etc., process text and graphics data using an input
apparatus such as a keyboard, a mouse or a digitizer.
The digitizer is for digitally detecting the position of a pen or a
finger on a flat panel specifically manufactured to output X and Y
coordinates of the position and has merits in that characters and
figures both can be input easily and accurately in comparison to a
conventional mouse, keyboard or scanner. Further, the digitizer is
envisioned to replace the conventional input devices.
The digitizer is classified into three types: a stylus type using a
specially devised pen; a finger touch type using a finger; and a
touch panel type using a common pen or any pointed object.
The stylus type is widely used in graphics or CAD applications. The
finger touch type is used in an apparatus adopting a touch screen
display. The touch panel type is used in a personal digital
assistance (PDA) or an electronic organizer.
To implement a digitizer system, a tablet for assigning coordinate
data, a pointing device such as a stylus, a pen or a finger for
locating a position on a coordinate system represented by the
tablet, and a digitizer controller for controlling the above
elements.
The tablet has a specially manufactured rectangular panel. The
panel is coated with a resistive film for the stylus type or the
finger touch type or is constituted by two sheets of resistive
material separated by a spacer and concurrently arranged to be
capable of contact by pressure for the touch panel type.
The location of the pointing device is recognized by the
differences in detected signals according to the pressed position
when an AC (the stylus and the finger touch types) or DC (the touch
panel type) signal is applied at the four corners of the panel.
Such a panel and controller are disclosed in U.S. Pat. Nos.
4,600,807, 4,649,232, 4,650,962 and 4,665,283, thus a description
thereof will be omitted.
However, since the conventional digitizer controller is
specifically designed for only one of the three types described
above, it is inconvenient to equip a corresponding digitizer
controller according to each type. Also, since the digitizer
controller is embodied with discrete circuit elements, the size of
the apparatus becomes large and power consumption is high.
DISCLOSURE OF THE INVENTION
To solve the above problems, it is an object of the present
invention to provide a digitizer controller which can be adopted
for each of the stylus, finger touch and touch panel types.
It is a second object of the present invention to provide an
improved driving method in the finger touch type.
It is a third object of the present invention to provide a driving
apparatus of the finger touch type befitting the above driving
method.
It is a fourth object of the present invention to provide a method
of automatically adjusting the band pass filtering characteristics
constituting the digitizer controller.
It is a fifth object of the present invention to provide an
apparatus for automatically adjusting the band pass filtering
characteristics constituting the digitizer controller.
It is a sixth object of the present invention to provide an
interfacing portion befitting the digitizer controller.
It is a seventh object of the present invention to provide a
generator of a panel driving signal befitting the digitizer
controller.
It is an eighth object of the present invention to provide a
generator of a panel driving control signal befitting the digitizer
controller.
It is a ninth object of the present invention to provide a power
saving circuit befitting the digitizer controller.
Accordingly, to achieve the first object there is provided a
digitizer controller comprising: a panel drive signal generator for
receiving a clock signal having a predetermined first frequency and
generating a panel drive signal having a predetermined second
frequency and required in the stylus and finger touch modes; a
reference voltage generator for generating a reference voltage
signal having a predetermined reference level required in a touch
panel mode; a first multiplexer for selectively outputting one of
the reference voltage signal provided from the reference voltage
generator and the panel drive signal provided from the panel drive
signal generator in response to a mode selection signal indicating
the stylus, finger touch or touch panel mode; a 4-channel driving
portion for receiving the output of the first multiplexer and
generating a channel driving signal which is provided to each
corner of the panel in response to the panel drive control signal
according to an operation mode; a current-voltage converter for
detecting a change in current in or out of each corner of the
panel; a differential amplifier for generating a differential
signal of four channels corresponding to the differential component
between the output of the current-voltage converter (18) and the
channel driving signal provided from the 4-channel driving portion
(16) in the finger touch mode; a second multiplexer (22) for
sequentially selecting the four-channel differential signal output
from the differential amplifier (20) to output the selected signal
as a finger touch signal; a third multiplexer (26) for selectively
outputting one of the finger touch signal output from the second
multiplexer (22) and a stylus signal output from a stylus in
response to the mode selection signal; a fourth multiplexer (34)
for selectively outputting one of a predetermined reference voltage
and the touch panel signal output from the panel (200) in response
to the mode selection signal; a band pass filter (28) for filtering
the frequency component of the panel drive signal from the output
of the third multiplexer (26); a rectifier (30) for rectifying the
output of the band pass filter (28); a fifth multiplexer for
selectively outputting one of the outputs of the rectifier and the
fourth multiplexer in response to the mode selection signal; a low
pass filter for detecting a substantial direct current component
from the output of the fifth multiplexer; an analog-to-digital
converter for converting the output of the low pass filter into a
digital signal in synchronization with the panel driving control
signal to output as a coordinates signal; and an interface for
receiving a control command provided from a microprocessor,
generating the mode selection signal indicating the stylus, the
finger touch or the touch panel mode by interpreting the received
control command and the panel driving control signal corresponding
to the selected mode, and transmitting the coordinates signal
provided from the analog-to-digital converter to the
microprocessor.
It is preferred in the present invention that the differential
amplifier is provided with a plurality of channel driving blocks
corresponding to the number of the channel driving signals, each
amplifying the difference of one of the channel driving signals and
one of the current-voltage converted channel driving signals.
It is also preferred in the present invention that the digitizer
controller further comprises a preamplifier for amplifying the
finger touch signal, the stylus signal and the touch panel signal
by a predetermined gain, respectively, to provide to one of the
third multiplexer and the fourth multiplexer.
It is also preferred in the present invention that the digitizer
controller further comprises: a direct current amplifier having
three direct current amplifiers for amplifying the output of the
low pass filter at separate gains according to the operation mode;
and a sixth multiplexer for selecting one of the outputs of the
direct current amplifiers in response to the mode selection signal
to provide the selected output to the analog-to-digital
converter.
It is also preferred in the present invention that the digitizer
controller further comprises a digital-to-analog converter for
converting the digital control signal provided from the
microprocessor into an analog signal to apply the converted control
signal as a frequency characteristic control signal of the band
pass filter.
It is also preferred in the present invention that the panel drive
signal generator further generates a pilot signal having
substantially the same frequency as that of the panel drive signal
which is provided to the band pass filter during automatic
frequency characteristic control.
It is also preferred in the present invention that the
current-voltage converter is configured with variable resistors so
that sensitivity of the current-voltage conversion can be
adjusted.
It is also preferred in the present invention that the bandwidth of
the low pas filter is narrow for removal of noise components and
conversion to direct current is easily achieved.
To achieve the second object there is provided a method for driving
a panel befitting a finger touch type digitizer comprising the
steps of applying channel driving signals having the same potential
to each corner of the panel; detecting the change in current
generated by the contact of a finger on the panel in or out of each
corner of the panel, and converting the detected change in current
changing into a change in voltage; detecting differential signals
corresponding to the difference of the current-to-voltage converted
signal and the channel driving signal; sequentially selecting the
differential signals at a predetermined period and time-division
multiplexing the selected differential signals; and determining the
contact position of the finger according to the size of the
multiplex differential signal.
To achieve the third object there is provided a driving apparatus
of a finger touch type digitizer comprising: a panel drive signal
generator for generating a panel drive signal required in a finger
touch mode; a 4-channel driving portion for receiving the panel
drive signal and generating a 4-channel driving signal of
substantially the same electric potential which is provided to the
four corners of a panel; a current-to-voltage converter, interposed
between the 4-channel panel driving portion and the panel, for
detecting a change in current in or out of each corner of the panel
when the finger contacts the panel; a differential amplifier for
generating a difference of the 4-channel driving signal and the
current-to-voltage conversion value from the current-to-voltage
converter; a multiplexer for sequentially selecting the
four-channel differential signal of the output from the
differential amplifier at a predetermined period to output the
selected signal; a band pass filter for detecting a frequency
component of the panel drive signal from the output of the
multiplexer; a low pass filter for extracting a substantial direct
current component from the output of the band pass filter; and an
analog-to-digital converter for converting the output of the low
pass filter into a digital signal in synchronization with the
selected period of the multiplexer.
To achieve the fourth object there is provided a method of
adjusting the frequency characteristic of a band pass filter for
band-pass-filtering a frequency component of a panel drive signal
from a finger touch signal provided from a panel or a stylus signal
provided from a stylus in a digitizer controller befitting a stylus
type and a finger touch type, the method comprising the steps of:
inputting a pilot signal having substantially the same frequency as
the panel drive signal to the band pass filter and continuously
converting within a predetermined range an adjusting signal for
adjusting the frequency characteristic of the band pass filter;
comparing the signal from the band pass filter and determining a
value of the adjustment signal having the maximum amplitude of the
detected signal; and setting a frequency characteristic of the band
pass filter according to the determined adjustment signal.
To achieve the fifth object there is provided an apparatus for
adjusting the frequency characteristic of a band pass filter for
band-pass-filtering a frequency component of a panel drive signal
from a finger touch signal provided from a panel or a stylus signal
provided from a stylus in a digitizer controller befitting a stylus
type and a finger touch type digitizer, the apparatus comprising: a
panel drive signal generator for generating a pilot signal having
substantially the same frequency as that of a panel drive signal to
provide to the band pass filter; a digital-to-analog converter for
converting an analog adjustment signal applied from a
microprocessor into an digital signal and applying the converted
signal as a signal for adjusting the frequency characteristic of
the band pass filter; an analog-to-digital converter for detecting
the amplitude of a signal from the band pass filter; a
microprocessor for generating the adjustment signal changing within
a predetermined range to change the frequency characteristic of the
band pass filter to provide the generated adjustment signal to the
digital-to-analog converter, determining an adjustment signal
corresponding to a signal having the maximum amplitude among the
band-pass-filtered signals from the changing adjustment signal
within the predetermined range, and providing the determined
adjustment signal as a frequency characteristic adjustment signal
of the band pass filter.
To achieve the sixth object there is provided an interface for
transmitting control commands generated from a microprocessor to
peripheral devices and controlling the transmission of the data
provided from the peripheral devices to the microprocessor, the
interface comprising: a data latch for latching the control command
provided from the microprocessor; a data buffer for inputting the
data provided from the peripheral devices and outputting the input
data to the microprocessor; a command decoder for receiving the
control command provided from the data latch and generating various
control signals necessary for control of the peripheral devices;
and an address decoder for receiving an address signal provided
from the microprocessor and generating signals for activating the
data latch and the data buffer.
To achieve the seventh object there is provided a digitizer
controller in which the panel drive signal generator comprises: a D
flip-flop for receiving a clock signal and generating a (n-1)th
signal divided by n, wherein n is an integer, and wherein the (n-1)
divided signal is generated, each being synchronized from the first
clock signal to the (n-1)th clock signal in a sequential clock
signal string of the corresponding number to division ratio n; a
ladder portion for generating a pseudo sinusoidal signal by
weight-calculating the (n-1) division signals according to a
predetermined resistance value; and a band pass filter for
generating the panel drive signal which is a substantial sine wave
by band-pass-filtering the pseudo sinusoidal signal provided from
the ladder portion.
To achieve the eighth object there is provided a digitizer
controller in which the panel driving control signal generator
comprises: a first counter for generating a first count signal by
counting the clock signal at a predetermined first counting ratio;
a second counter for binary-counting the first count signal
provided from the first counter to output the binary-counted signal
as a second signal; an inverting portion having two inverters for
respectively inverting the first and second count signals each
provided from the first and second counters; an OR gate for OR-ing
the first and second count signals; and a signal selecting portion
for receiving the first and second count signals respectively
provided from the first and second counters, the inverted first and
second count signals provided from the inverting portion and a
signal output from the OR gate and generating a panel driving
control signal corresponding to each mode in response to the mode
selection signal, wherein the signal selecting portion outputs the
first and second count signals respectively provided from the first
and second counters, the inverted first and second count signals
provided from the inverting portion and a signal output from the OR
gate in the stylus and the touch panel modes and the signal
provided from the OR gate in the finger touch mode.
To achieve the ninth object there is provided a digitizer
controller further comprising: a counting portion for counting the
clock signal having a predetermined period at a predetermined first
count ratio to output a first pulse signal; a counter for counting
the first pulse signal output from the counting portion at a
predetermined second count ratio, by starting the counting
operation according to a tip signal of the stylus; and a power slip
signal generator for determining whether the idle status of the
stylus continues over a predetermined time period by AND-ing a
second pulse signal output from the counter and the tip signal of
the stylus and generating a power slip signal for controlling power
consumption if the idle status continues over the predetermined
time period, wherein the interface enters a power saving mode in
response to the power slip signal provided from the power slip
signal generator.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a digitizer controller according
to a preferred embodiment of the present invention;
FIGS. 2A and 2B show the waveforms of the panel drive control
signals and channel drive signals, respectively, illustrating the
operation of the digitizer controller shown in FIG. 1 in a stylus
mode;
FIG. 3 is a diagram schematically illustrating the signal flow in
the digitizer controller shown in FIG. 1 in the stylus mode;
FIGS. 4A through 4E are waveforms illustrating the operation of
each constituent element of the digitizer controller show in FIG. 1
in the stylus mode;
FIGS. 5A and 5B show the waveforms of the panel drive control
signals and channel drive signals, respectively, in the operation
of a conventional digitizer controller of a finger touch mode;
FIGS. 6A and 6C are graphs showing the waveforms of the panel drive
control signals and channel drive signals, respectively, in the
operation of the digitizer controller of the present invention
shown in FIG. 1 in a finger touch mode;
FIG. 7 is a diagram schematically illustrating the signal flow in
the digitizer controller shown in FIG. 1 in the finger touch
mode;
FIGS. 8A through 8E show the waveforms in the operation of each
constituent element of the digitizer controller shown in FIG. 1 in
the finger touch mode;
FIGS. 9A and 9B show the waveforms of the panel drive control
signals and channel drive signals, respectively, in the operation
of the digitizer controller shown in FIG. 1 in a touch panel
mode;;
FIG. 10 is a diagram schematically illustrating the signal flow in
the digitizer controller shown in FIG. 1 in the touch panel
mode;
FIGS. 11A to 11C show the waveforms in the operation of each
constituent element of the digitizer controller shown in FIG. 1 in
the touch panel mode;
FIG. 12 is a diagram showing the format of the mode select signal
shown in FIG. 1;
FIG. 13 is a diagram showing the panel drive signal generator shown
in FIG. 1;
FIGS. 14A-14G show the waveforms of signals illustrating the
operation of the device shown in FIG. 13;
FIG. 15 is a schematic block diagram of a conventional panel
driving signal generating device;
FIG. 16 is a detailed schematic block diagram of the 4-channel
panel driving portion shown in FIG. 1;
FIG. 17 is a detailed schematic block diagram of the differential
amplifying portion shown in FIG. 1;
FIG. 18 is a detailed schematic block diagram of the band pass
filter and the digital-to-analog converter shown in FIG. 1;
FIGS. 19A and 19B are graphs showing the frequency characteristics
of the band pass filter shown in FIG. 18;
FIG. 20 illustrates the format of an adjusting signal for adjusting
the frequency characteristics of the band pass filter shown in FIG.
18;
FIG. 21 illustrates signal flow in an automatic
frequency-characteristic adjusting mode;
FIG. 22 illustrates the conversion in the analog-to-digital
converter shown in FIG. 1;
FIG. 23 is a detailed schematic block diagram of the interface
portion shown in FIG. 1;
FIGS. 24A-24H are timing diagrams of signals, for showing the
operation of the device shown in FIG. 23;
FIG. 25 is a block diagram of another embodiment of the digitizer
controller according to the present invention;
FIG. 26 is a detailed schematic block diagram of the power save
device shown in FIG. 25;
FIGS. 27A-28D illustrate the waveforms of signals for showing the
operation of the power save device shown in FIG. 26;
FIG. 29 is a detailed schematic block diagram of the panel driving
control signal generating portion shown in FIG. 25; and
FIG. 30 is a layout view of integrated circuits for realizing the
device of FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram of a digitizer controller according to a
preferred embodiment of the present invention. In FIG. 1, reference
numeral 100 represents a digitizer controller according to the
present invention, reference numeral 200 represents a panel, and
reference numeral 300 represents a stylus.
The digitizer controller 100 includes a panel drive signal
generator 10, a reference voltage generator 12, a first multiplexer
(MUX) 14, a four-channel panel driver 16, a current-to-voltage
converter 18, a differential amplifier 20, a second multiplexer 22,
a preamplifier 24, a third multiplexer 26, a band pass filter (BPF)
28, a rectifier 30, a digital-to-analog (D/A) converter 32, a
fourth multiplexer 34, a fifth multiplexer 36, a low pass filter
(LPF) 38, a direct current (DC) amplifier 40, a sixth multiplexer
42, an analog-to-digital converter (A/D) 44, and an interface
portion 46.
The panel drive signal generator 10 generates a predetermined panel
drive signal 48 of a second frequency for driving a panel 200 in a
stylus or finger touch mode and a pilot signal 50 for adjusting
frequency characteristics of the BPF 28, using a clock of a
predetermined first frequency signal applied thereto. Here, in the
stylus mode the digitizer controller 100 operates so that it is
suited to a stylus type, and in the finger touch mode the digitizer
controller 100 operates so that it is suited to a finger touch
type. Preferably, the panel drive signal 48 and the pilot signal 50
are sinusoidal having a predetermined period.
The reference voltage generator 12 generates a reference voltage
signal 52 for driving the panel 200 on the touch panel mode. Here,
in the touch panel mode the digitizer controller 100 operates so
that it is suited to a touch panel type. Here, the reference
voltage signal 52 is a DC signal with a first reference voltage of
a predetermined value.
The first multiplexer 14 selectively outputs the panel driving
signal 48 provide from the panel drive signal generator 10 and the
reference voltage signal 52 provided from the reference voltage
generator 12 according to a mode select signal applied thereto.
The four-channel panel driver 16 receives the channel drive signal
48 or the reference signal 52 output from the first multiplexer 14
and generates channel driving signals UL, UR, LL and LR which are
suitable for the stylus mode, finger touch mode and touch channel
mode in response to panel drive control signals C.sub.-- UL,
C.sub.-- UR, C.sub.-- LL and C.sub.-- LR applied thereto. Here, the
channel drive signals UL, UR, LL and LR for the first to the fourth
channels are provided to the upper left, upper right, lower left
and lower right corners of the panel 200, respectively.
The current-to-voltage converter 18 includes current-to-voltage
converting portions (generally, resistors) each applied to the four
channel drive signals UL, UR, LL and LR, which detect the change in
current input to or output from each corner of the panel 200 in the
touch panel mode.
The differential amplifier 20 outputs signals DIFF.sub.-- UR,
DIFF.sub.-- UL, DIFF.sub.-- LR and DIFF.sub.-- LL corresponding to
each difference between the channel drive signals UL, UR, LL and LR
and current-to-voltage-converted signals UL', UR', LL' and LR'
output from the current-to-voltage converter 18. That is, the
signals DIFF.sub.-- UR, DIFF.sub.-- UL, DIFF.sub.-- LR and
DIFF.sub.-- LL each have an amplitude corresponding to the
difference each between UR and UR', UL and UL', LR and LR', and LL
and LL'.
The second multiplexer 22 selectively outputs one of the signals
DIFF.sub.-- UR, DIFF.sub.-- UL, DIFF.sub.-- LR and DIFF.sub.-- LL
provided from the differential amplifier 20 according to a channel
select signal applied thereto. That is, the second multiplexer 22
outputs the signals DIFF.sub.-- UR, DIFF.sub.-- UL, DIFF.sub.-- LR
and DIFF.sub.-- LL for time segments T1, T2, T3 and T4,
respectively.
The signal (finger touch signal 58) output from the second
multiplexer 22, the signal (touch panel signal 62) output from the
panel 200, and the signal (stylus signal 60) output from the stylus
300 are provided to the preamplifier 24.
The preamplifier 24 includes three sub-preamplifiers 24a, 24b and
24c each of which amplify the finger touch signal 58, stylus signal
60 and touch panel signal 62 with different gains,
respectively.
The finger touch signal 58 amplified by the first sub-preamplifier
24a and the stylus signal 60 amplified by the second
sub-preamplifier 24b are provided to the third multiplexer 26, and
the touch panel signal 62 amplified by the third sub-preamplifier
24c is provided to the fourth multiplexer 34.
The third multiplexer 26 selectively outputs one of the pilot
signal 50 output from the panel drive signal generator 10 and
finger touch signal 58 output from the panel 200 and stylus signal
60 output from the stylus 300 according to the mode select signal
applied thereto.
The BPF 28 band-pass filters the sequence component of the panel
drive signal from the output of the third multiplexer 26 to remove
undesirable noise.
A filtered signal 64 output from the BPF 28 is rectified by the
rectifier 30 and then provided as an input to the fifth multiplex
36.
The fourth multiplexer 34 selectively outputs a predetermined
reference voltage (ground voltage) or the amplified touch panel
signal 62 according to the mode select signal applied thereto and
provides the selected signal as the other input to the fifth
multiplexer 36.
The fifth multiplexer 36 selectively outputs a signal 66 output
from the rectifier 30 or a signal output from the fourth
multiplexer 34 according to the mode select signal applied
thereto.
The LPF 38 low-pass filters the signal output from the fifth
multiplexer 36 for making the signal into a direct current (DC) and
outputs the result to the DC amplifier 40. Here, preferably, the
bandwidth of the LPF 38 is narrow. If the band width is wide, many
alternating current (AC) components are output, thereby
destabilizing the output value. Thus, the AC components should be
removed by narrowing the bandwidth as much as possible.
The DC amplifier 40 includes three sub-DC amplifiers 40a, 40b and
40c which are applied to the finger touch mode, stylus mode and
touch panel mode, respectively. Each sub-DC amplifier amplifies the
signal output from the LPF 38 and outputs the amplified signal.
Here, since different gains are required in each mode, the proper
sub-DC amplifier should be selected according to each mode.
The sixth multiplexer 42 selectively outputs one of the signals
output from the sub-DC amplifiers 40a, 40b and 40c to the AID
converter 44 according to the mode select signal applied
thereto.
The A/D converter 44 converts the analog signal 70 output from the
sixth multiplexer 42 into a digital signal according to a clock
signal and control signal applied thereto and outputs the converted
digital signal to the interface portion 46.
The interface portion 46 controls the above-described constituent
elements according to a control signal provided from a
microprocessor (not shown) and transmits the digital signal
converted by the A/D converter 44 to the microprocessor.
The digital signal transmitted to the microprocessor is a digital
coordinate signal with respect to the stylus, pen and finger from
the panel 200.
The operation of the digitizer controller shown in FIG. 1 in the
stylus mode, finger touch mode and touch panel mode will be
described as follows.
First, the operation of the four-channel panel driver 16 shown in
FIG. 1 in the stylus mode will be described with reference to FIGS.
2A and 2B which are diagrams showing waveforms of the panel drive
control signals C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.--
LR, and channel drive signals UL, LL, UR and LR, respectively.
The panel drive control signals C.sub.-- UL, C.sub.-- LL, C.sub.--
UR and C.sub.-- LR shown in FIG. 2A are digital signals. Here, high
levels (VH) of these signals indicate that the channel drive
signals UL, LL, UR and LR are applied to each corner of the panel
200, and low levels (VL) indicate that a predetermined DC voltage
(preferably, ground) is applied to each corner of the panel 200.
Also, the panel drive control signals C.sub.-- UL, C.sub.-- LL,
C.sub.-- UR and C.sub.-- LR shown from top to bottom of FIG. 2A,
respectively, correspond to the channel drive signals UL, LL, UR
and LR shown from top to bottom of FIG. 2B, respectively.
In order to recognize one set of coordinates where the stylus is
located, the four corners of the panel 200 are driven four times in
pairs of two corners per drive. Here, the left and right corners
are driven prior to the upper and lower corners. For example, when
the channel drive signals UL and LL are applied to the upper left
and lower left corners of the panel 200 and a ground potential is
applied to the remaining corners as shown in interval T1, the
amplitude of the signal detected by the stylus moving on the panel
200 corresponds to a distance x.sup.+ from the right edge of the
panel to the position of the stylus. Also, when the channel drive
signals UR and LR are applied to the upper right and lower right
corners of the panel 200 and ground is applied to the remaining
corners as shown in interval T2, the amplitude of the signal
detected by the stylus corresponds to a distance x.sup.- from the
left edge of the panel to the position of the stylus.
That is, the x-coordinate is determined as a relative coordinate by
the following formula (1). ##EQU1##
The amplitude of the signal in interval T1 corresponds to x.sup.+
and the amplitude of the signal in interval T2 corresponds to
x.sup.-, respectively. Thus, the x-coordinate is recognized by the
amplitude ratio between x.sup.+ and x.sup.-. In the same manner,
y.sup.+ and y.sup.- are detected in interval T3 and T4, and then
y-coordinate is recognized by the amplitude ratio between y.sup.+
and y.sup.-. That is, the y-coordinate is determined as a relative
coordinate by the following formula (2). ##EQU2##
This method for determining the x- and y-coordinates is disclosed
in U.S. Pat. Nos. 4,600,807, 4,649,232, 4,650,962 and
4,665,283.
In the stylus mode, the mode select signal represents the stylus
mode. As a result, the first multiplexer 14 selectively outputs the
panel drive signal 48 output from the panel drive signal generator
10, the third multiplexer 26 selectively outputs the stylus signal
60 output from the second sub-preamplifier 24b, the fifth
multiplexer 36 selectively output the signal 66 output from the
rectifier 30, and the sixth multiplexer 42 selectively outputs the
signal output from the second sub-DC amplifier 40b.
FIG. 3 illustrates the signal flow in the stylus mode. Here, the
interface portion 46 generates a mode select signal, a panel drive
control signal, an adjusting signal and a channel select signal
under the control of the microprocessor. The panel drive signal 48
output from the panel drive signal generator 10 is provided to the
four-channel panel driver 16 via the first multiplexer 14. The
four-channel panel driver 16 generates the channel drive signals
UL, LL, UR and LR shown in FIG. 2B in accordance with the panel
drive control signals C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and
C.sub.-- LR shown in FIG. 2A and outputs the generated signals to
each corner of the panel 200. The stylus signal detected by the
stylus 300 from the panel 200 is provided to the second
sub-preamplifier 24b. The pre-amplified stylus signal 60 output
from the second sub-preamplifier 24b is provided to the BPF 28 via
the third multiplexer 26. The BPF 28 extracts a component having
the frequency of the panel drive signal as a main frequency from
the stylus signal 60 and outputs the extracted signal to the
rectifier 30, and then the rectifier 30 rectifies the extracted
signal and then output the rectified signal. The signal 66 output
from the rectifier 30 is provided to the LPF 38 via the fifth
multiplexer 36. The LPF 38 low-pass filters the signal 66 output
from the rectifier 30 and outputs the result to the second sub-DC
amplifier 40b. The second sub-DC amplifier 40b amplifies the signal
68 output from the LPF 38 and outputs the amplified signal to the
A/D converter 44 via the sixth multiplexer 42. The A/D converter 44
converts the signal 70 output from the sixth multiplexer 42 into a
digital signal and then the digital signal is output to the
interface portion 46 via a data bus 104. Here, the converted
digital signal is a signal which represents the amplitude of the
signal detected by the stylus distances x.sup.+, x.sup.-, y.sup.+
and y.sup.- from the location of stylus to each side of the panel
200 in interval T1, T2, T3 and T4. The interface portion 46
provides the coordinate signal output from the AID converter 44 via
a bus 102 to the microprocessor.
FIGS. 4A through 4E are waveforms illustrating the operation of
each constituent element of the digitizer controller shown in FIG.
1 in the stylus mode. More specifically, FIG. 4A is a waveform of
the clock signal input to the panel drive signal generator 10, FIG.
4B is a waveform of the panel drive signal 48 generated by the
panel drive signal generator 10 using the clock signal shown in
FIG. 4A, FIG. 4C are waveforms of the panel drive control signals
C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.-- LR applied to
the four-channel panel driver 16, FIG. 4D shows an example of the
waveform of the stylus signal 60 at a point detected by the stylus,
and FIG. 4E is a waveform of the signal 68 output from the LPF
38.
Next, the operation of the digitizer controller according to the
present invention in the finger touch mode will be described.
According to a preferred embodiment, the driving method of the
digitizer controller in the finger touch mode is different from
that of the conventional digitizer controller. According to the
conventional driving method, four corners of the panel are driven
one at a time. Also, in the stylus mode or the touch panel mode,
while two corners of the panel are driven simultaneously in the
digitizer controller of the present invention, the channel drive
signal is applied to only one corner in the conventional digitizer
controller, so that less current is detected. Accordingly, the
sensitivity of the differential amplifier should be increased.
In the driving method of the present invention, the channel drive
signals UL, LL, UR and LR each having the same amplitude are
simultaneously applied to four corners of the panel and the change
in current detected by each channel is detected in sequence,
thereby improving the sensitivity of the digitizer controller of
the present invention.
The operation of the digitizer controller in the finger touch mode
will be described in detail with reference to FIGS. 5A, 5B and
6A-6C.
FIG. 5A shows waveforms of the panel drive control signals C.sub.--
UL, C.sub.-- LL, C.sub.-- UR and C.sub.-- LR of the conventional
digitizer controller in the finger touch mode. As shown in FIG. 5A,
only one corner of the panel is driven in each of sections T1, T2,
T3 and T4 when a change in the current in each channel is detected.
FIG. 5B shows waveforms of the channel drive signals UL, LL, UR and
LR generated in accordance with the panel drive control signals
C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.-- LR shown in FIG.
5A.
FIGS. 6A through 6C illustrate the driving method of the digitizer
controller according to the present invention in the finger touch
mode. FIG. 6A shows waveforms of the panel drive control signals
C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.-- LR in the finger
touch mode according to the driving method of the present digitizer
controller.
As shown in FIG. 6A, the four corners of the panel are all driven
in sections T1, T2, T3 and T4 when a change in current in each
channel is detected. Accordingly, the change in current in each
channel is increased, thereby improving the sensitivity. FIG. 6B
shows waveforms of the channel drive signals UL, LL, UR and LR
generated in accordance with the panel drive control signals
C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.-- LR shown in FIG.
6A, and FIG. 6C shows waveforms of the channel select signal. Here,
a change current in each channel is detected in sections T1, T2, T3
and T4 one at a time according to the channel select signal.
The driving method of the digitizer controller in the finger touch
mode according to the present invention is as follows.
First, the channel drive signals UL, LL, UR and LR each having an
AC component with the same potential are simultaneously applied to
all four corners of the panel.
Second, the change in current which is generated by the contact of
a finger on the panel and input to/output from each corner of the
panel is detected and then converted into a change in voltage.
Third, differential signals which correspond to the amplitude
difference between the channel drive signals UL, LL UR and LR, and
the current-to-voltage-converted signals are detected.
Fourth, the differential signals are repeatedly selected with a
predetermined period in sequence and then a time division
multiplexing is performed with respect to the selected signals.
Finally, the position of the finger on the panel 200 is determined
on the basis of the amplitude of the multiplexed difference
signal.
In the finger touch mode, the channel drive signals UL, LL, UR and
LR each having the same phase and amplitude are applied to all four
corners of the panel 200. When a finger touches the panel, the
current input to/output from each corner of the panel 200 is
changed according to the position of the finger on the panel 200
since the finger functions as a capacitor located between the
ground and the panel. Then, the current-to-voltage converter 18
converts the change in current into a change in voltage, and
outputs the result.
In the finger touch mode, the mode select signal represents the
finger touch mode. Accordingly, the first multiplexer 14
selectively outputs the panel drive signal 48 output from the panel
drive signal generator 10, the second multiplexer 22 selectively
outputs the differential signals selected in sequence, the third
multiplexer 26 selectively outputs the finger touch signal 58
output from the first sub-preamplifier 24a, the fifth multiplexer
36 selectively outputs the signal 66 output from the rectifier 30,
and the sixth multiplexer 42 selectively outputs the signal output
from the first sub-DC amplifier 40a.
FIG. 7 shows the signal flow in the finger touch mode.
The interface portion 46 generates a mode select signal, a panel
drive control signal, an adjusting signal and a channel select
signal under the control of the microprocessor.
The panel drive signal 48 output from the panel drive signal
generator 10 is provided to the four-channel panel driver 16 via
the first multiplexer 14.
The four-channel panel driver 16 generates the channel drive
signals UL, LL, UR and LR shown in FIG. 6B in accordance with the
panel drive control signals C.sub.-- UL, C.sub.-- LL, C.sub.-- UR
and C.sub.-- LR shown in FIG. 6A and outputs the generated signals
to each corner of the panel 200.
The current-to-voltage-converted channel drive signals UL', LL',
UR' and LR', which change according to the position of the finger
on the panel 200, are provided to the differential amplifier 20,
and the differential signals output from the differential amplifier
20 are selected by the second multiplexer 22 in sequence. Then, the
selected signal is provided to the first sub-preamplifier 24a as
the finger touch signal 58.
The finger touch signal pre-amplified by the first sub-preamplifier
24a is provided to the BPF 28 via the third multiplexer 26.
The BPF 28 extracts a component having the frequency of the panel
drive signal 48 as a main frequency from the finger touch signal 58
and outputs the extracted signal to the rectifier 30, and then the
rectifier 30 rectifies the extracted signal and then outputs the
rectified signal.
The signal 66 output from the rectifier 30 is provided to the LPF
38 via the fifth multiplexer 36.
The LPF 38 low pass filters the signal 66 output from the rectifier
30 and outputs the result to the first sub-DC amplifier 40a.
The first sub-DC amplifier 40a amplifies the signal 68 output from
the LPF 38 and outputs the amplified signal to the A/D converter 44
via the sixth multiplexer 42.
The A/D converter 44 converts the signal 70 output from the sixth
multiplexer 42 into a digital signal and then the digital signal is
output to the interface portion 46 via the data bus 104.
The interface portion 46 provides the coordinate signal output from
the A/D converter 44 via the bus 102 to the microprocessor.
FIGS. 8A through 8E are waveforms illustrating the operation of
each constituent element of the digitizer controller show in FIG. 1
in the finger touch mode. More specifically, FIG. 8A is a waveform
of the clock signal input to the panel drive signal generator 10,
FIG. 8B is a waveform of the panel drive signal 48 generated by the
panel drive signal generator 10 using the clock signal shown in
FIG. 8A, FIG. 8C are waveforms of the panel drive control signals
C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.-- LR applied to
the four-channel panel driver 16, FIG. 8D shows an example of the
waveform of the finger touch signal output from the second
multiplexer 22, and FIG. 8E is a waveform of the signal 68 output
from the LPF 38.
Next, the operation of the four-channel panel driver 16 shown in
FIG. 1 in the touch panel mode will be described with reference to
FIGS. 9A and 9B, wherein FIG. 9A are waveforms of the panel drive
control signals C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and C.sub.--
LR and FIG. 9B are waveforms of the channel drive signals UL, LL,
UR and LR, respectively.
In the touch panel mode, all four corners of the panel 200 are
driven by a DC signal differently from the stylus mode. However,
the panel drive control signals C.sub.-- UL, C.sub.-- LL, C.sub.--
UR and C.sub.-- LR in the touch panel mode are the same as those in
the stylus mode. A signal generated by the touch of a pen on the
panel 200 is detected by the panel 200. In the same manner as the
stylus mode, the x-coordinate of the position of the pen is
recognized in sections T1 and T2, and the y-coordinate of the
position of the pen is recognized in sections T3 and T4,
respectively. A reference voltage signal required for the touch
panel mode is provided from the reference voltage generator 12.
In the touch panel mode, the mode select signal represents the
touch panel mode. Accordingly, the first multiplexer 14 selectively
outputs the reference voltage signal output from the reference
voltage generator 12, the fourth multiplexer 34 selectively outputs
the pre-amplified touch panel signal output from the third
sub-preamplifier 24c, the fifth multiplexer 36 selectively outputs
the signal output from the fourth multiplexer 34, and the sixth
multiplexer 42 selectively outputs the signal output from the third
sub-DC amplifier 40c.
FIG. 10 schematically shows the signal flow in the touch panel
mode.
The interface portion 46 generates a mode select signal, a panel
drive control signal, an adjusting signal and a channel select
signal under the control of the microprocessor.
The reference voltage signal generated from the reference voltage
generator 12 is provided via the first multiplexer 14 to the
four-channel panel driver 16.
The four-channel panel driver 16 generates the channel drive
signals UL, LL, UR and LR shown in FIG. 9B in accordance with the
panel drive control signals C.sub.-- UL, C.sub.-- LL, C.sub.-- UR
and C.sub.-- LR shown in FIG. 9A and outputs the generated signals
to each corner of the panel 200.
The touch panel signal 62 detected by the panel according to the
location of the pen (not shown) moving on the panel 200 is provided
to the third sub-preamplifier 24c.
The touch panel signal 62 pre-amplified by the third
sub-preamplifier 24c is provided to the LPF 38 via the fifth
multiplexer 36. Then, the third sub-DC amplifier 40c amplifies the
signal 68 provided from the LPF 38 and provides the amplified
signal to the A/D converter 44 via the sixth multiplexer 42.
The A/D converter 44 converts the signal 70 output from the sixth
multiplexer 42 into a digital signal and then the digital signal is
output to the interface portion 46. The interface portion 46
provides the coordinate signal output from the A/D converter 44 to
the microprocessor.
FIGS. 11A through 11C are waveforms illustrating the operation of
each constituent element of the digitizer controller shown in FIG.
1 in the touch panel mode. More specifically, FIG. 11A are
waveforms of the reference voltage signal generated from the
reference voltage generator 12, FIG. 11B are waveforms of the panel
drive control signals C.sub.-- UL, C.sub.-- LL, C.sub.-- UR and
C.sub.-- LR applied to the four-channel panel driver 16, and FIG.
11C shows an example of the waveform of the touch panel signal
detected by the panel 200.
FIG. 12 shows a mode select signal for controlling the selection
operation of the first multiplexer 14, the four-channel panel
driver 16, the third multiplexer 25, the fourth multiplexer 34, the
fifth multiplexer 36 and the sixth multiplexer 42. The mode
selection signal is a two-bit digital signal. In FIG. 12, the mode
selection operation is controlled by the combination of the bit 0
in the upper portion of the graph and the bit 1 in the lower
portion. That is, "00" of the mode selection signal value
represents a stylus mode, "10" thereof represents a finger touch
mode, and "01" thereof represents a touch panel mode,
respectively.
FIG. 13 is a detailed structural diagram of the panel drive signal
generator 10 shown in FIG. 1. The structure shown in FIG. 13 which
is described in Korean Patent Application No. 95-15442 by the
present applicant is incorporated into the present invention.
A panel driving signal generating portion shown in FIG. 13 includes
a D flip-flop portion 120, an amplifying portion 122, a ladder
portion 124, a band pass filter 126, and an amplifier 128.
The D flip-flop portion 120 receives clock signals and generates
(n-1) signals whose frequencies are divided into n sections (n is
an integer). Here, the (n-1) frequency-divided signals are
synchronized with the first to the (n-1)th clock signals of a clock
signal sequence, respectively.
In a suggested embodiment, there are four cascading D flip-flops
120a-120d. That is, the non-inverted output of each previous D
flip-flop is supplied as the input the following D flip-flop, the
inverted output of the last D flip-flop is supplied as the input of
the first D flip-flop, and three frequency-divided signals are
obtained from the non-inverted outputs of the first three D
flip-flops.
Here, the numbers of frequency-divided signals and corresponding
D-flip-flops are related to the resolution of an intended panel
driving signal. To simulate a panel driving signal in three steps,
for instance, three delay signals and four D-flip-flops are
required.
Here, the number of required D flip-flops, n, is the same as the
number of steps in which the panel driving signal is expressed.
The amplifying portion 122 has amplifiers 122a-122c for
differentially amplifying the frequency-divided signals output from
the D-flip-flop portion 120.
The ladder portion 124 generates a pseudo-sinusoidal signal by
adding the frequency-divided signals output from the amplifying
portion 122 according to their respective resistances of resistors
124a, 124b, 124c, 124d and 124e. Here, the pseudo-sinusoidal signal
indicates a signal having a waveform approximate to that of an
ideal sine wave signal.
The band pass filter (BPF) 126 band pass filters the
pseudo-sinusoidal signal output from the ladder portion 124, and
generates the pilot signal 50 for the BPF 28 shown in FIG. 1.
The amplifier 128 generates the panel driving signal 48 to the
first multiplexer 14 of FIG. 1 by amplifying a signal output from
the BPF 126.
FIGS. 14A-14G illustrate the waveforms of signals for describing
the operation of the panel driving signal generating portion shown
in FIG. 13, in a case of a sine wave signal represented in three
steps. FIG. 14A illustrate a clock signal CLOCK, FIG. 14B
illustrates a clear signal CLEAR, and FIGS. 14C-14E illustrate
frequency-divided signals V1, V2, and V3, respectively. FIG. 14F
illustrates the pseudo-sinusoidal signal output from the ladder
portion 124, and FIG. 14G illustrates the signal output from the
BPF 126.
FIG. 15 schematically illustrates a conventional panel driving
signal generating device. The device of FIG. 15 has a counter 140
for counting clock signals, a decoder 142 for decoding the counted
signals from the counter 140 and generating a plurality of
switching control signals, a plurality of current sources 144a-144n
to be enabled or disenabled in response to the control signals
output from the decoder 142, respectively, and an amplifying
portion 146 for obtaining the sum of currents generated in the
plurality of current sources 144a-144n.
The panel driving signal generating device of FIG. 15 is
disadvantaged in that it has overly large circuits, high power
dissipation, and difficulty in circuit integration. Also, since the
counted value of the clock signals must inconveniently be decoded,
as many current sources as there are decoded bits are required.
In contrast, due to the advantage of not requiring a counter, a
decoder, and current sources, the panel driving signal generating
circuit of the present invention shown in FIG. 13 is simpler and
exhibits lower power consumption, thus being suitable for a sine
wave generating circuit realized in the form of an integrated
circuits.
FIG. 16 is a detailed schematic block diagram of the 4-channel
panel driving portion and the current-voltage converting portion
shown in FIG. 1. The 4-channel panel driving portion 16 includes
four driving blocks 16a-16d for generating channel driving signals
UL, UR, LL, and LR, respectively, to the four corners of the panel
200. The respective driving blocks 16a-16d receive panel driving
control signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and C.sub.--
LR and a signal output from the first multiplexer 14, and outputs
the channel driving signals UL, UR, LL, and LR to the four corners
of the panel 200. The channel driving signals UL, UR, LL, and LR
output from the 4-channel panel driving portion 16 are supplied to
the four corners of the panel 200 via the current-voltage
converting portion 18.
The current-voltage converting portion 18 has four variable
resistors 18a-18d for current-voltage converting the channel
driving signals UL, UR, LL, and LR provided to the four corners. In
a finger touch mode, by varying resistance, the resistors 18a-18d
can adjust the sensitivity.
FIG. 17 schematically illustrates the differential amplifying
portion 20 and the second multiplexer 22 shown in FIG. 1, in
detail. The differential amplifying portion 20 has four
differential amplifiers 20a-20d for receiving the channel driving
signals 54, i.e., UL, UR, LL, and LR output from the 4-channel
panel driving portion 16 and current-voltage converted channel
driving signals 56 supplied from the current-voltage converting
portion 18, and generating their difference signals 57.
FIG. 18 is a detailed schematic block diagram of the BPF 28 and the
digital-to-analog converter 32 shown in FIG. 1. In FIG. 18, the BPF
28 is provided with a low-pass notch (LPN) filter 28a, a high-pass
notch (HPN) filter 28b, and a BPF 28c.
FIG. 19A illustrates normal frequency characteristics of the BPF
shown in FIG. 18. Here, reference characters A, B, and C indicate
the frequency characteristic of the LPN filter 28a, the HPN filter
28b, and the BPF 28c, respectively.
The central frequency of the BPF having the frequency
characteristics indicated by A, B, and C should be adjusted to the
frequency of the panel driving signal 48.
In a process for manufacturing the digitizer controller of the
present invention, the characteristics of the filters 28a, 28b, and
28c may drift depending on the distribution of process parameters.
For example, they may drift up and down desirable frequency
characteristic curves, as shown in FIG. 19B as portions A', B', and
C' indicated by dotted lines or portions A", B", and C" indicated
by one-dot-dashed lines. -Such drifts deteriorate the reliability
of the digitizer controller, for example, performance degrades in
terms of noise elimination and amplification degree. To prevent
this problem, a special approach is taken in the present
invention.
A method for adjusting the frequency characteristics of a BPF
according to the present invention is implemented as follows.
First, a pilot signal having the same frequency, in a practical
sense, as that of a panel driving signal is input to the BPF, and a
signal for adjusting the frequency characteristics of the BPF is
continuously varied within a predetermined range.
Then, the value of a signal for adjusting the frequency
characteristics of a detected signal which has the largest
magnitude is determined by comparing the magnitudes of signals from
the BPF.
Finally, the frequency characteristics of the BPF are determined by
the determined frequency-characteristic adjusting signal.
The digital-to-analog converter 32 generates analog signals for
adjusting the frequency characteristics of the filters 28a, 28b,
and 28c shown in FIG. 18.
The digital-to-analog signal converter 32 converts an adjusting
signal output from a microprocessor into an analog signal and
outputs the analog signal to the LPN filter 28a, the HPN filter
28b, and the BPF 28c.
FIG. 20 illustrates the format of the signal for automatically
adjusting frequency characteristics output from the microprocessor
to the digital-to-analog converter 32. Bit groups 32a, 32b, and 32c
move the central frequencies of the LPN filter 28a, the HPN filter
28b, and the BPF 28c.
FIG. 21 illustrates the flow of a signal in an automatic
frequency-characteristic adjusting mode. Here, the automatic
frequency-characteristic adjusting mode can be implemented at
moment power is initially applied to the digitizer controller.
In the automatic frequency-characteristic adjusting mode, the third
multiplexer 26 selects the pilot signal 50 output from the panel
drive signal generator 10 in response to a mode select signal. The
microprocessor supplies the automatic frequency-characteristic
adjusting signal to the digital-to-analog converter 32.
The BPF 28 band-pass filters the pilot signal 50 by frequency
characteristics adjusted by an analog signal output from the
digital-to-analog converter 32. The rectifier 30 receives the
filtered pilot signal 50 and rectifies it.
The signal 66 output from the rectifier 30 is supplied to the low
pass filter 38 via the fifth multiplexer 36.
The low pass filter 38 low-pass filters the signal 66 output from
the rectifier 30 and outputs the filtered signal to the second DC
amplifier 40b.
The second DC amplifier 40b amplifies the signal 68 output from the
low pass filter 38 and outputs the amplified signal to the
analog-to-digital converter 44 via the sixth multiplexer 42.
The analog-to-digital converter 44 converts the signal 70 output
from the sixth multiplexer 42 into a digital signal and outputs the
digital signal to the interface portion 46.
The interface portion 46 outputs the converted digital signal to
the microprocessor via the bus 102.
The microprocessor sequentially provides adjusting signals varying
in a predetermined range to the digital-to-analog converter 32 and
compares the results. An adjusting signal having the largest
resulting value is determined as a result of the comparison and
output as a finally determined frequency-characteristic adjusting
signal to the interface portion 46. A data latch (not shown) in the
interface portion 46 latches the adjusting signal and outputs the
latched signal to the digital-to-analog converter 32. The
digital-to-analog converter 32 determines the frequency
characteristics of the BPF according to the adjusting signal
latched by the latch.
The automatically frequency-characteristic adjusting method as
described above is advantageous in that, for example, the frequency
characteristics of the BPF 28 may undesirably drift by the
distribution of process parameters, or the sensitivity of a device
may vary due to a variation in the frequencies of the panel driving
signal 48 generated in the panel drive signal generator 10 and the
pilot signal 50, in other cases.
However, since the panel driving signal 48 and the pilot signal 50
have the same frequency, adjustment of the frequency
characteristics of the BPF 28 by the pilot signal 50 enables the
central frequency of the BPF 28 to be accurately adjusted to the
frequency of the panel driving signal 48.
The analog-to-digital converter 44 receives complementary dual
inputs and digitally converts their difference. That is, the
analog-to-digital converter 44 receives complementary signals and
digitally converts their difference to a predetermined resolution.
In the embodiment of the present invention, as shown in FIG. 22,
the range of dual input is 1-4V (the center voltage is 2.5V), and
the resolution is 2.sup.12. In the embodiment of the present
invention, the analog-to-digital converter 44 outputs twelve bits
of "1111 1111 1111" in the case of the dual input difference being
4V, "1000 0000 0000" in the case of 0V, and "0000 0000 0000" in the
case of -4V.
FIG. 23 is a detailed schematic block diagram of the interface
portion shown in FIG. 1. The device shown in FIG. 23 is
incorporated in the present invention and described in Korea Patent
Application No. 95-21316 by the present applicant entitled System
Control Signal Transmitting Circuit.
The device of FIG. 23 has a command decoder 46a, a data latch 46b,
an address decoder 46c, and a data buffer 46d.
The microprocessor (not shown) supplies a system write control
signal WRITE, a system read control signal READ, a clock signal
CLOCK, a power save enable signal PSEN, an address signal ADDRESS,
an automatic frequency-characteristic adjusting signal, panel
driving control signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and
C.sub.-- LR, a channel select signal, an analog-to-digital
converter controlling signal, and instruction data to the interface
portion 46 via the bus 102. The interface portion 46 outputs
digital data expressed in terms of coordinates, which was converted
by the analog-to-digital converter 44 and the resulting value of
the BPF corresponding to the frequency-characteristic adjusting
signal to the microprocessor.
The data latch 46b and the data buffer 46d have unique addresses
which can be assigned by the microprocessor.
The address decoder 46c receives an address signal from the
microprocessor and generates a signal for activating the data
buffer 46d or the data latch 46b.
When the data latch 46b is activated by the address decoder 46c, it
latches a control instruction received from the microprocessor.
The command decoder 46a receives the control instruction latched in
the data latch 46b, and generates the mode select signal, the panel
driving control signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and
C.sub.-- LR, the channel select signal, and the automatic
frequency-characteristic adjusting signal, which are needed for
controlling the digitizer controller shown in FIG. 1.
In the embodiment shown in FIG. 1, the panel driving control
signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and C.sub.-- LR are
generated in the microprocessor, and output to the 4-channel panel
driving portion 16 via the interface portion 46. The microprocessor
generates the panel driving control signals C.sub.-- UL, C.sub.--
UR, C.sub.-- LL, and C.sub.-- LR by a software by using data stored
in a memory (not shown) such as a ROM. The panel driving signals
can be obtained in a later-described another panel driving control
signal generating device.
When the data buffer 46d is activated by the address decoder 46c,
it receives digitally converted data from the analog-to-digital
converter 44, or outputs stored coordinate values to the
microprocessor via the bus 102.
The input and output operations of the interface portion 46,
especially, the data latch 46b or the data buffer 46d, are
controlled by the system write control signal and the system read
control signal supplied via the bus 102.
When the system write control signal is activated, the data latch
46b of the interface portion 46 receives instruction data from the
microprocessor, and the instruction decoder 46a decodes the
instruction data, thereby controlling the operation of the
digitizer controller.
When the system read control signal is activated, the data buffer
46d of the interface portion 46 receives a digital signal from the
analog-to-digital converter 44. The digital data received in the
data buffer 46d is transmitted to the microprocessor. Here, the
conversion of the analog-to-digital converter 44 is performed by
synchronization with the system read control signal.
FIGS. 24A-24H are timing diagrams of signals, for showing the
operations of the interface portions shown in FIG. 23. FIG. 24A
illustrates the procedure of the address signal ADDRESS loaded on
the bus 102, and a control instruction and adjusting signal COMMAND
and ADC, FIG. 24B illustrates the power save enable signal PSEN,
FIG. 24C illustrates an address latch enable signal ALE, FIG. 24D
illustrates the system write control signal WRITE, FIG. 24E
illustrates the system read control signal READ, FIG. 24F
illustrates the state of an address latched by the address decoder
46c, FIG. 24G illustrates transmission of system control signals
output from the instruction decoder 46a, and FIG. 24H illustrates
digital data converted in the analog-to-digital converter 44.
Referring to FIGS. 24A-24H, the addresses indicative of the data
latch 46b and the data buffer 46c, the control instruction, and the
automatic frequency-characteristic adjusting signal are transmitted
via the bus 102.
When the power save enable signal PSEN and the address latch enable
signal ALE are high, the address decoder 46c receives an address
transmitted via the bus 102, decodes the address, and activates the
data latch 46b or the data buffer 46d.
In the figures, ADDRESS1 and ADDRESS2 indicate the addresses of the
data latch 46b and the data buffer, respectively.
When the address signal represents ADDRESS1 and the system write
control signal is low, the data latch 46b receives the control
instruction transmitted via the bus 102, and the instruction
decoder 46a decodes the control instruction and outputs various
system control signals.
When the address represents ADDRESS2 and the system read control
signal is low, the data buffer 46d receives digital data from the
analog-to-digital converter 44 and transmits the digital data to
the microprocessor. In practice, the data latch 46b is constituted
by, a plurality of latches (not shown). Each inter-latch has a
unique address for a direct access of the microprocessor. The
addresses of the data latch 46b and the interlatches are
hierarchically arranged. Such latches can be provided, for example,
for the mode select signal, the panel driving control signals
C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and C.sub.-- LR, the
frequency-characteristics adjusting signal, and the channel select
signal, respectively.
FIG. 25 illustrates another embodiment of the digitizer controller
500 according to the present invention. The device of FIG. 25 is
the same as that of FIG. 1, except that a panel drive control
signal generating portion 74 and a power saving control circuit 72
are further provided. Thus, the description of like elements will
be omitted.
The digitizer controller 100 shown in FIG. 1 is controlled by the
power save enable signal output from the microprocessor. Thus, the
microprocessor determines by a software whether a power save mode
is set. This imposes constraints on the microprocessor and requires
a signal transmission line for transmitting the power save enable
signal between the microprocessor and the digitizer controller
100.
On the other hand, to circumvent the above problem, in the
digitizer controller 500 shown in FIG. 25, the power saving control
circuit 72 is provided to determine whether a power save mode is
set according to a tip signal TIP generated in the stylus 300.
Then, when the power saving control circuit 72 generates a power
slip signal, the interface portion 46 sets the digitizer controller
in the power save mode.
FIG. 26 is a detailed schematic block diagram of the power saving
control circuit 72 of FIG. 25. The structure shown in FIG. 26 which
is described in Korean Patent Application No. 95-56423 by the
present applicant is incorporated into the present invention.
The power saving control circuit 72 has a counting portion 720 for
counting clock signals and outputting a pulse signal having a
predetermined period, and a power slip signal generating portion
722 for generating the power slip signal PSL for controlling power
consumption when the panel is idle for longer than a predetermined
time.
The counting portion 720 includes a first counter 720a for counting
clock signal and a second counter 720b for counting the output of
the first counter.
The power slip signal generating portion 722 includes a switch 722a
for controlling the transmission of the pulse signal output from
the second counter 720b in response to the TIP signal from the
stylus 300, a third counter 722b for counting the outputs of the
switch 722a, and an AND gate 722c for performing a logic
multiplication on the output of the third counter 722b and the
signal TIP. Here, the signal TIP is generated in the stylus 300.
When the point of the stylus 300 contacts the panel, the signal TIP
becomes high, otherwise, the signal is low.
FIGS. 27A through 28D illustrate the waveforms of signals in the
operation of the power save device shown in FIG. 26. FIG. 27A
illustrates the waveform of the clock signal, FIG. 27B illustrates
the waveform of a clear signal, and FIG. 27C illustrates the output
of the second counter 720b.
The first and second counters 720a and 720b count the clock signal
shown in FIG. 27A, and the second counter 720b outputs a first
pulse signal Q1 having a predetermined period. The first pulse
signal Q1 is output from a carry-of-bit (COB) terminal provided to
the counter.
In the suggested embodiment, the clock signal is 2 MHz, the first
counter 720a is a duodecimal counter, and the second counter 720b
is a quaternary counter. Therefore, the frequency of the first
pulse signal Q1 output from the second counter 720b is 244 Hz.
FIG. 28A illustrates the waveform of the pulse signal Q1 output
from the second counter 720b, FIG. 28B illustrates the waveform of
the signal TIP output from the stylus 300, FIG. 28C illustrates the
waveform of a pulse signal Q2 output from the third counter 722b,
and FIG. 28D illustrates the waveform of the power slip signal PSL
output from the AND gate 722d.
As shown in FIGS. 28A-28D, when the signal TIP is high, the third
counter 722b counts the first pulse signal Q1, and outputs the
second pulse signal Q2 of a high level when the counting is
completed. When the signal TIP and the second pulse signal Q2 are
both high, the power slip signal PSL output from the AND gate 722c
becomes high.
This power slip signal PSL is provided via the interface portion
46. When the power slip signal PSL is generated, the interface
portion 46 sets the digitizer controller 500 shown in FIG. 25 in
the power save mode.
The digitizer controller 100 of FIG. 1 is controlled by the panel
driving control signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and
C.sub.-- LR output from the microprocessor. Hence, the
microprocessor generates the panel driving control signals C.sub.--
UL, C.sub.-- UR, C.sub.-- LL, and C.sub.-- LR depending on the mode
by a memory such as a ROM or by a software. This imposes
constraints on the microprocessor, and requires a 4-bit signal
transmission line for transmitting the panel driving control
signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and C.sub.-- LR
between the microprocessor and the digitizer controller 100.
On the other hand, the digitizer controller of FIG. 25 has a block
74 for generating the panel driving control signals C.sub.-- UL,
C.sub.-- UR, C.sub.-- LL and C.sub.-- LR required according to the
mode select signal output from the microprocessor, thus overcoming
the above problem.
FIG. 29 is a detailed schematic block diagram of the panel driving
control signal generating circuit shown in FIG. 25. The device of
FIG. 29 is incorporated in the present invention, a part of which
is described in Korean Patent Application No. 95-69704 entitled
Panel Driving Circuit for Pen Digitizer.
The device of FIG. 29 has a first counter 740, a second counter
742, an inverting portion 744, an OR gate 746, and a signal
selecting portion 748.
The first counter 740 duodecimally counts a clock signal.
Here, the period of a first count signal output from the first
counter 740 corresponds to that of the panel driving control
signals C.sub.-- LL and C.sub.-- UR for controlling the channel
driving signals LL and UR provided to the lower left and the upper
right portions of the panel 200.
The second counter 742 binarily counts the first count signal
output from the first counter 740. Here, the period of a second
count signal corresponds to that of the panel driving control
signals C.sub.-- UL and C.sub.-- LR for controlling the channel
driving signals UL and LR provided to the upper left and the lower
right portions of the panel 200.
The inverter portion 744 has two inverters 744a and 744b for
inverting the first count signal output from the first counter 740
and the second count signal output from the second counter 742.
The OR gate 746 generates a logic addition signal of the first
count signal output from the first counter 740, the second count
signal output from the second counter 742, an inverted first count
signal output from the first inverter 746a, and an inverted second
count signal output from the second inverter 746b.
The signal selecting portion 748 generates the panel driving
control signals C.sub.-- UL, C.sub.-- UR, C.sub.-- LL, and C.sub.--
LR corresponding to modes in response to the mode select signal.
For example, when the mode select signal represents a stylus mode
or a touch panel mode, the signal selecting portion 748 selectively
outputs the first count signal output from the first counter 740,
the second count signal output from the second counter 742, the
inverted first count signal output from the first inverter 746a,
and the inverted second count signal output from the second
inverter 746b. If the mode select signal represents the finger
touch, mode, the signal selecting portion 748 selectively outputs
the signals supplied from the OR gate 746.
FIG. 30 illustrates a layout of integrated circuits for realizing
the device shown in FIG. 1. In the suggested embodiment, the
microprocessor 400 has a capacity of 8 bits. Data is transmitted
between the microprocessor and the interface portion 46 via the
8-bit bus. There are signal lines for transmitting the system write
control signal, the system read control signal, the address latch
enable signal, the clock signal, the power save enable signal, and
the panel driving control signals C.sub.-- UL, C.sub.-- UR,
C.sub.-- LL, and C.sub.-- LR.
As described above, the digitizer controller has the following
advantages: (1) it can operate in any of a stylus mode, a finger
touch mode, and a touch panel mode; (2) since it can be realized in
integrated circuits, power dissipation is small; and (3) it can
automatically adjust the frequency characteristics of a BPF,
thereby increasing the reliability and enabling the realization of
an automatic multi-functional digitizer system.
INDUSTRIAL APPLICABILITY
The digitizer controller of the present invention can be used in
graphics or CAD applications a touch screen display, a personal
digital assistance or an electric organizer. The digitizer
controller can be implemented into a semiconductor integrated
circuit.
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